Method of treatment of porous wallboard



Sept. 14, 1965 E. NUORIVAARA METHOD OF TREATMENT OF POROUS WALLBOARDFiled March 21, 1961 United States Patent O 3,206,346 METHOD OFTREATMENT OF POROUS WALL-BOARD Ensio Nuorivaara, Kuopio, Finland FiledMar. 21, 1961, Ser. No. "97,290 Claims priority, application Finland,Nov. 19, 1960,

1,913/ 60 p v Claims. '(Cl. 156209) This invention refers to a method ofreducing the dimensional changes taking place in the plane of porouswallboard due to moisture variation and the stresses resultingtherefrom.

It is known, that an undesirable property of porous wallboard is thedimensional variation thereof caused by variations of moisture. Themoisture in the board is somewhat greater during storage than when theboard is fixed to the base surface underneath. If the board is glued toa rigid base, such "as a concrete wall, a .plastered surface or the likeand the moisture in the same varies slightly there will be formed in theboard stresses that are so great that the base surface, the glue or theboard itself will give way, with the result that the board comes loosefrom its support.

In order to prevent the board from loosening from a rigid, solidfoundation, the fastening of the board is often carried by nailing thesame to a wooden frame assembly which is secured to the base. The boardsfixed in this manner are able to move sufliciently where the nail holesare situated to compensate for dimensional variation. This manner offastening, however has several disadvantages. In the first place themethod becomes rather expensive due to the necessary construction of awooden frame, secondly it reduces the area of the room and thirdly thereis left a large space between the board and the foundation underneath,which from the danger of fire makes the house unsafe.

In order to overcome the above drawbacks there has been suggested theuse of an intermediate flexible element which will permit thedimensional changes in the board. Such intermediate flexible element maybe a flexible plastic glue which secures the board to the base. Suchmethods of fastening are expensive however and between the board and thebase there is also left an air space.

There has been additionally suggested the use of a panelling slab whichby means of grooves can be made to yield in such a degree that the slabis allowed freely to breathe during the different stages of moisture, inwhich case there would not be any stresses in the slab. This methodseems to be the best of the known methods, but even this has thedisadvantage that it requires a great deal of glue and the forming ofthe grooves is rather difficult.

The present invention has as its principal object to provide wallboardof the above stated kind which is free from all the above stateddisadvantages. A characteristic feature of the invention is that theboard is suitably compressed momentarily to a thickness less than halfof its original thickness, such that its internal strucure is altered.

A board treated according to this invention can without furthertreatment be fastened to a base surface by means of gluing. Hereafterthe board has insufficient strength to tear itself free from its base,because the internal structure of the board has been changed such thatthe fibers are no longer interconnected as effectively as before andwill give way to a certain extent.

According to one very advantageous embodiment of the invention the boardis pressed for an instant to a thickness equal to less than half of theoriginal thickness.

3,206,346 Patented Sept. 14, 1965 ice After being treated in the abovemanner the changes in the dimension of the board owing to moisturevariation will be only /3 of that of the original board and the internalstrength will be only of the strength of the original board.

The invention is further illustrated by thespeci'fication and thedrawing showing an embodiment which 'is most adaptable in the practice,in which drawing FIG. 1 shows .a pressing :operation in the treatment ofa board,

FIG. 2 shows the surface ofa treated board, and

FIG. 3 shows a section taken .along line JII"IIII in FIG. 2.

In the drawing the numeral 1 designates an ordinary porous wallboardwhichis fed along by the top roller 2 and the bottom roller 3 in adirection shown by the arrow 4. Simultaneously these rollers press theboard just for an "instant so that the thickness of the :board becomesless than half of the original thickness. The pressing period is shortso that the change in the form of the board 1 is not permanent and theboard will attain its original thickness.

The surface of the top roller 2 is provided with elevations or teeth 5,between which there is formed excavations 6. These teeth and excavationsconstitute an effective means whereby the inner structure of the board 1can be changed while simultaneously the surface of the board is madedecorative in order to meet the demands for internal panelling of aroom. FIGURES 2 and 3 illustrate an embodiment in the arrangement of theelevations and excavations formed on the surface of the board 1.

In the event the porous wallboard is intended to be used for insidepanelling, it is appropriate to cover one or both of its sides with alayer of material such as paper, cloth, metal or the like. The fasteningof such layer to the board can most suitably be performed simultaneouslywith the pressing operation. For this purpose the surface of the boardis covered with a layer or film of glue, and on top of this adhesivelayer the said covering layer is placed before the board is fed betweenbetween the rollers 2 and 3. In order to expedite the binding propertiesin the glue it is advisable to heat one or both of the rollers. Theheating of the rollers will also harden the elevations and excavations.

The layer on the surface of the board also provides additional stiffnessto the board and improves its external appearance. Furthermore the layerprevents moisture from entering into the board. Especially when a metalouter layer is used, such as aluminum, is the moisture totally preventedfrom penetrating into the board.

The above is intended only to illustrate the inventive idea of theinvention. The different embodiments adaptable in practical use may thusvary while remaining within the limits of the following claims. Thisrefers especially to how thin the board has to be pressed during thetreatment, and this again depends on how great the moisture changes arethat the board has to withstand at the place where it is to be used.

Also the number of rollers may vary. In certain cases it is preferableto perform the pressing of the board between several successive pairs ofrollers, between which the board is pressed gradually with increasedpressure.

What is claimed is:

1. A method of treating a porous compressible fibre board ofdeterminable thickness to provide dimensional stability thereof undermoisture variation, said method comprising deforming the internalstructure of the board by momentarily and temporarily compressing theboard to a thickness which is less than half the original thickness ofthe board and allowing the board to resiliently 3 assume its originalthickness immediately after the cornpressing of the board;

2. A method of treating a porous fibre board of determinable thickness,said method comprising deforming the internal structure of the board byadvancing said board between a pair of rollers which are spaced apart adistance which is less than one half the thickness of the board wherebysaid board is momentarily and temporarily compressed to a thickness lessthan one half the original thickness of the board as the board passesbetween the rollers, and allowing said board to assume substantially itsoriginal thickness after it passes through said rollers, the deformingof the internal structure of the board under the compression of therollers and the subsequent assumption of its original thicknessconferring on said fibre board dimensional stability when exposed tovarying humidity conditions.

3. A method as claimed in claim 2 wherein one of said rollers isprovided with teeth to locally intensify the compression of said board.

4. A method as claimed in claim 2 comprising adherently fixing acovering layer on at least one of the surfaces of said board prior tothe advancement through said rollers so that the layer is simultaneouslycompressed with the board.

5. A method as claimed in claim 4 comprising heating said rollers toprovide an elevated temperature thereof.

References Cited by the Examiner UNITED STATES PATENTS 2,136,730 11/38Sweetland 156-580 2,477,300 7/49 Karfiol et al.

2,537,126 1/51 Francis 15447 2,600,843 6/52 Bush.

2,694,026 11/54 Johnson 161-165 2,711,380 6/55 Pintell.

2,859,489 11/58 Morrison 161156 2,954,838 10/60 Nuorivaara 11711 FOREIGNPATENTS 821,537 10/59 Great Britain.

EARL M. BERGERT, Primary Examiner.

CARL F. KRAFFT, Examiner.

Loetscher 15443

2. A METHOD OF TREATING A POROUS FIBRE BOARD OF DETERMINABLE THICKNESS,SAID METHOD COMPRISING DEFORMING THE INTERNAL STRUCTURE OF THE BOARD BYADVANCING SAID BOARD BETWEEN A PAIR OF ROLLERS WHICH ARE SPACED APART ADISTANCE WHICH IS LESS THAN ONE HALF THE THICKNESS OF THE BOARD WHEREBYSAID BOARD IS MOMENTARILY AND TEMPORARILY COMPRESSED TO A THICKNESS LESSTHAN ONE HALF THE ORIGINAL THICKNESS OF THE BOARD AS THE BOARD PASSESBETWEEN THE ROLLERS, AND ALLOWING SAID BOARD TO ASSUME SUBSTANTIALLY ITSORIGINAL THICKNESS AFTER IT PASSES THROUGH SAID ROLLERS, THE DEFORMINGOF THE INTERNAL STRUCTURE OF THE BOARD UNDER THE COMPRESSION OF THEROLLERS AND THE SUBSEQUENT ASSUMPTION OF ITS ORIGINAL THICKNESSCONFERRING ON SAID FIBRE BOARD DIMENSIONAL STABILITY WHEN EXPOSED TOVARYING HUMIDITY CONDITIONS.